/*
 * Copyright (C) 2011 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package dk.dr.radio.net.volley;

import android.os.SystemClock;

import com.android.volley.Cache;
import com.android.volley.VolleyLog;

import java.io.EOFException;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.regex.Pattern;

import dk.dr.radio.diverse.App;
import dk.dr.radio.diverse.Log;
import dk.dr.radio.net.Diverse;

/**
 * Cache-implementering, der cacher filerne direkte på harddisken.
 * I modsætning til Volleys standardimplementation har denne her en meget lav opstartstid
 * Vi kunne have arvet fra DiskBasedCache hvis mEntries havde været protected
 */
public class DrDiskBasedCache implements Cache {

  /** Map of the Key, CacheHeader pairs */
  private final Map<String, CacheHeader> mEntries =
      new LinkedHashMap<String, CacheHeader>(16, .75f, true);
  /** Total amount of space currently used by the cache in bytes. */
  private long mTotalSize = 0;

  /** The root directory to use for the cache. */
  private final File mRootDirectory;

  /** The maximum size of the cache in bytes. */
  private final int mMaxCacheSizeInBytes;

  /** Default maximum disk usage in bytes. 1MB cache burde være rigeligt */
  private static final int DEFAULT_DISK_USAGE_BYTES = 1 * 1024 * 1024; // DR ÆNDRING

  /** High water mark percentage for the cache */
  private static final float HYSTERESIS_FACTOR = 0.9f;

  /** Magic number for current version of cache file format. */
  private static final int CACHE_MAGIC = 0x20120504;

  /**
   * Constructs an instance of the DiskBasedCache at the specified directory.
   * @param rootDirectory       The root directory of the cache.
   * @param maxCacheSizeInBytes The maximum size of the cache in bytes.
   */
  public DrDiskBasedCache(File rootDirectory, int maxCacheSizeInBytes) {
    mRootDirectory = rootDirectory;
    mMaxCacheSizeInBytes = maxCacheSizeInBytes;
    //mRootDirectory.mkdirs();
  }

  /**
   * Constructs an instance of the DiskBasedCache at the specified directory using
   * the default maximum cache size of 5MB.
   * @param rootDirectory The root directory of the cache.
   */
  public DrDiskBasedCache(File rootDirectory) {
    this(rootDirectory, DEFAULT_DISK_USAGE_BYTES);
  }

  /**
   * Clears the cache. Deletes all cached files from disk.
   */
  @Override
  public synchronized void clear() {
    sletFilerÆldreEnd(0);
  }

  /**
   * Fjerner gamle filer. DrVolleyDiskBasedCache opdaterer løbende tidsstempel på de filer, der bruges,
   * så det er kun gamle UBRUGTE filer, der fjernes.
   * @param tidsstempel filer ændret før dette tidspunkt slettes.
   * @return antal byte der blev slettet
   */
  public int sletFilerÆldreEnd(long tidsstempel) {
    mEntries.clear();
    mTotalSize = 0;
    return Diverse.sletFilerÆldreEnd(mRootDirectory, tidsstempel);
  }

  /**
   * Returns the cache entry with the specified key if it exists, null otherwise.
   */
  @Override
  public synchronized Entry get(String key) {
    CacheHeader entry = mEntries.get(key);
    File file = getFileForKey(key);
    if (entry == null && !file.exists()) { // DR ÆNDRING
      // if the entry does not exist, return.
      if (App.fejlsøgning) Log.d("DrVolleyDiskBasedCache miss for " + key);
      return null;
    }

    boolean ny = entry == null; // DR ÆNDRING
    CountingInputStream cis = null;
    try {
      cis = new CountingInputStream(new FileInputStream(file));
      CacheHeader nyEntry = CacheHeader.readHeader(cis); // eat header
      byte[] data = streamToBytes(cis, (int) (file.length() - cis.bytesRead));
      if (ny) { // DR ÆNDRING
        if (App.fejlsøgning) Log.d("DrVolleyDiskBasedCache fil0-hit for " + key);
        entry = nyEntry;
        entry.size = file.length();
        putEntry(entry.key, entry);
        file.setLastModified(System.currentTimeMillis()); // Opdatér tidsstempel så vi kan se den er blevet brugt
      } else {
        if (App.fejlsøgning) Log.d("DrVolleyDiskBasedCache fil1-hit for " + key);
      }
      return entry.toCacheEntry(data);
    } catch (IOException e) {
      VolleyLog.d("%s: %s", file.getAbsolutePath(), e.toString());
      remove(key);
      return null;
    } finally {
      if (cis != null) {
        try {
          cis.close();
        } catch (IOException ioe) {
          return null;
        }
      }
    }
  }

  /**
   * Initializes the DiskBasedCache by scanning for all files currently in the
   * specified root directory. Creates the root directory if necessary.
   */
  @Override
  public synchronized void initialize() {
    if (!mRootDirectory.exists()) {
      if (!mRootDirectory.mkdirs()) {
        VolleyLog.e("Unable to create cache dir %s", mRootDirectory.getAbsolutePath());
      }
    }
/* DR ÆNDRING - løb ikke igennem cache-mappen, det tager henved 1 sekund per 100 elementer
        File[] files = mRootDirectory.listFiles();
        if (files == null) {
            return;
        }
        for (File file : files) {
            FileInputStream fis = null;
            try {
                fis = new FileInputStream(file);
                CacheHeader entry = CacheHeader.readHeader(fis);
                entry.size = file.length();
                putEntry(entry.key, entry);
            } catch (IOException e) {
                if (file != null) {
                   file.delete();
        }
            } finally {
                try {
                    if (fis != null) {
                        fis.close();
    }
                } catch (IOException ignored) { }
            }
        }
        */
  }

  /**
   * Invalidates an entry in the cache.
   * @param key        Cache key
   * @param fullExpire True to fully expire the entry, false to soft expire
   */
  @Override
  public synchronized void invalidate(String key, boolean fullExpire) {
    Entry entry = get(key);
    if (entry != null) {
      entry.softTtl = 0;
      if (fullExpire) {
        entry.ttl = 0;
      }
      put(key, entry);
    }

  }

  /**
   * Puts the entry with the specified key into the cache.
   */
  @Override
  public synchronized void put(String key, Entry entry) {
    pruneIfNeeded(entry.data.length);
    File file = getFileForKey(key);
    try {
      FileOutputStream fos = new FileOutputStream(file);
      CacheHeader e = new CacheHeader(key, entry);
      e.writeHeader(fos);
      fos.write(entry.data);
      fos.close();
      putEntry(key, e);
      return;
    } catch (IOException e) {
      Log.e(e);
    }
    boolean deleted = file.delete();
    if (!deleted) {
      VolleyLog.d("Could not clean up file %s", file.getAbsolutePath());
    }
  }

  /**
   * Removes the specified key from the cache if it exists.
   */
  @Override
  public synchronized void remove(String key) {
    boolean deleted = getFileForKey(key).delete();
    removeEntry(key);
    if (!deleted) {
      VolleyLog.d("Could not delete cache entry for key=%s, filename=%s",
          key, getFilenameForKey(key));
    }
  }

  private static final String NORMALT_PRÆFIX = "http://www.dr.dk/tjenester/mu-apps/";
  private static final Pattern ULOVLIGE_TEGN_I_FILNAVN = Pattern.compile("[^a-zA-Z0-9_.-]");

  /**
   * Creates a pseudo-unique filename for the specified cache key.
   * @param key The key to generate a file name for.
   * @return A pseudo-unique filename.
   */
  private String getFilenameForKey(String key) {
    if (key.startsWith(NORMALT_PRÆFIX)) key = key.substring(NORMALT_PRÆFIX.length()); // DR ÆNDRING
    //key = key.replace('?', '_').replace('/', '_').replace('&', '_');
    // sikrere (og hurtigere?) er
    key = ULOVLIGE_TEGN_I_FILNAVN.matcher(key).replaceAll("_"); // DR ÆNDRING
    return key;
      /*
        int firstHalfLength = key.length() / 2;
        String localFilename = String.valueOf(key.substring(0, firstHalfLength).hashCode());
        localFilename += String.valueOf(key.substring(firstHalfLength).hashCode());
        return localFilename;
        */
  }

  /**
   * Returns a file object for the given cache key.
   */
  public File getFileForKey(String key) {
    return new File(mRootDirectory, getFilenameForKey(key));
  }

  /**
   * Prunes the cache to fit the amount of bytes specified.
   * @param neededSpace The amount of bytes we are trying to fit into the cache.
   */
  private void pruneIfNeeded(int neededSpace) {
    if ((mTotalSize + neededSpace) < mMaxCacheSizeInBytes) {
      return;
    }
    if (VolleyLog.DEBUG) {
      VolleyLog.v("Pruning old cache entries.");
    }

    long before = mTotalSize;
    int prunedFiles = 0;
    long startTime = SystemClock.elapsedRealtime();

    Iterator<Map.Entry<String, CacheHeader>> iterator = mEntries.entrySet().iterator();
    while (iterator.hasNext()) {
      Map.Entry<String, CacheHeader> entry = iterator.next();
      CacheHeader e = entry.getValue();
      boolean deleted = getFileForKey(e.key).delete();
      if (deleted) {
        mTotalSize -= e.size;
      } else {
        VolleyLog.d("Could not delete cache entry for key=%s, filename=%s",
            e.key, getFilenameForKey(e.key));
      }
      iterator.remove();
      prunedFiles++;

      if ((mTotalSize + neededSpace) < mMaxCacheSizeInBytes * HYSTERESIS_FACTOR) {
        break;
      }
    }

    if (VolleyLog.DEBUG) {
      VolleyLog.v("pruned %d files, %d bytes, %d ms",
          prunedFiles, (mTotalSize - before), SystemClock.elapsedRealtime() - startTime);
    }
  }

  /**
   * Puts the entry with the specified key into the cache.
   * @param key   The key to identify the entry by.
   * @param entry The entry to cache.
   */
  private void putEntry(String key, CacheHeader entry) {
    if (!mEntries.containsKey(key)) {
      mTotalSize += entry.size;
    } else {
      CacheHeader oldEntry = mEntries.get(key);
      mTotalSize += (entry.size - oldEntry.size);
    }
    mEntries.put(key, entry);
  }

  /**
   * Removes the entry identified by 'key' from the cache.
   */
  private void removeEntry(String key) {
    CacheHeader entry = mEntries.get(key);
    if (entry != null) {
      mTotalSize -= entry.size;
      mEntries.remove(key);
    }
  }

  /**
   * Reads the contents of an InputStream into a byte[].
   */
  private static byte[] streamToBytes(InputStream in, int length) throws IOException {
    byte[] bytes = new byte[length];
    int count;
    int pos = 0;
    while (pos < length && ((count = in.read(bytes, pos, length - pos)) != -1)) {
      pos += count;
    }
    if (pos != length) {
      throw new IOException("Expected " + length + " bytes, read " + pos + " bytes");
    }
    return bytes;
  }

  /**
   * Handles holding onto the cache headers for an entry.
   */
  // Visible for testing.
  static class CacheHeader {
    /**
     * The size of the data identified by this CacheHeader. (This is not
     * serialized to disk.
     */
    public long size;

    /** The key that identifies the cache entry. */
    public String key;

    /** ETag for cache coherence. */
    public String etag;

    /** Date of this response as reported by the server. */
    public long serverDate;

    /** TTL for this record. */
    public long ttl;

    /** Soft TTL for this record. */
    public long softTtl;

    /** Headers from the response resulting in this cache entry. */
    public Map<String, String> responseHeaders;

    private CacheHeader() {
    }

    /**
     * Instantiates a new CacheHeader object
     * @param key   The key that identifies the cache entry
     * @param entry The cache entry.
     */
    public CacheHeader(String key, Entry entry) {
      this.key = key;
      this.size = entry.data.length;
      this.etag = entry.etag;
      this.serverDate = entry.serverDate;
      this.ttl = entry.ttl;
      this.softTtl = entry.softTtl;
      this.responseHeaders = entry.responseHeaders;
    }

    /**
     * Reads the header off of an InputStream and returns a CacheHeader object.
     * @param is The InputStream to read from.
     * @throws IOException
     */
    public static CacheHeader readHeader(InputStream is) throws IOException {
      CacheHeader entry = new CacheHeader();
      int magic = readInt(is);
      if (magic != CACHE_MAGIC) {
        // don't bother deleting, it'll get pruned eventually
        throw new IOException();
      }
      entry.key = readString(is);
      entry.etag = readString(is);
      if (entry.etag.equals("")) {
        entry.etag = null;
      }
      entry.serverDate = readLong(is);
      entry.ttl = readLong(is);
      entry.softTtl = readLong(is);
      entry.responseHeaders = readStringStringMap(is);
      return entry;
    }

    /**
     * Creates a cache entry for the specified data.
     */
    public Entry toCacheEntry(byte[] data) {
      Entry e = new Entry();
      e.data = data;
      e.etag = etag;
      e.serverDate = serverDate;
      e.ttl = ttl;
      e.softTtl = softTtl;
      e.responseHeaders = responseHeaders;
      return e;
    }


    /**
     * Writes the contents of this CacheHeader to the specified OutputStream.
     */
    public boolean writeHeader(OutputStream os) {
      try {
        writeInt(os, CACHE_MAGIC);
        writeString(os, key);
        writeString(os, etag == null ? "" : etag);
        writeLong(os, serverDate);
        writeLong(os, ttl);
        writeLong(os, softTtl);
        writeStringStringMap(responseHeaders, os);
        os.flush();
        return true;
      } catch (IOException e) {
        VolleyLog.d("%s", e.toString());
        return false;
      }
    }

  }

  private static class CountingInputStream extends FilterInputStream {
    private int bytesRead = 0;

    private CountingInputStream(InputStream in) {
      super(in);
    }

    @Override
    public int read() throws IOException {
      int result = super.read();
      if (result != -1) {
        bytesRead++;
      }
      return result;
    }

    @Override
    public int read(byte[] buffer, int offset, int count) throws IOException {
      int result = super.read(buffer, offset, count);
      if (result != -1) {
        bytesRead += result;
      }
      return result;
    }
  }

    /*
     * Homebrewed simple serialization system used for reading and writing cache
     * headers on disk. Once upon a time, this used the standard Java
     * Object{Input,Output}Stream, but the default implementation relies heavily
     * on reflection (even for standard types) and generates a ton of garbage.
     */

  /**
   * Simple wrapper around {@link InputStream#read()} that throws EOFException
   * instead of returning -1.
   */
  private static int read(InputStream is) throws IOException {
    int b = is.read();
    if (b == -1) {
      throw new EOFException();
    }
    return b;
  }

  static void writeInt(OutputStream os, int n) throws IOException {
    os.write((n >> 0) & 0xff);
    os.write((n >> 8) & 0xff);
    os.write((n >> 16) & 0xff);
    os.write((n >> 24) & 0xff);
  }

  static int readInt(InputStream is) throws IOException {
    int n = 0;
    n |= (read(is) << 0);
    n |= (read(is) << 8);
    n |= (read(is) << 16);
    n |= (read(is) << 24);
    return n;
  }

  static void writeLong(OutputStream os, long n) throws IOException {
    os.write((byte) (n >>> 0));
    os.write((byte) (n >>> 8));
    os.write((byte) (n >>> 16));
    os.write((byte) (n >>> 24));
    os.write((byte) (n >>> 32));
    os.write((byte) (n >>> 40));
    os.write((byte) (n >>> 48));
    os.write((byte) (n >>> 56));
  }

  static long readLong(InputStream is) throws IOException {
    long n = 0;
    n |= ((read(is) & 0xFFL) << 0);
    n |= ((read(is) & 0xFFL) << 8);
    n |= ((read(is) & 0xFFL) << 16);
    n |= ((read(is) & 0xFFL) << 24);
    n |= ((read(is) & 0xFFL) << 32);
    n |= ((read(is) & 0xFFL) << 40);
    n |= ((read(is) & 0xFFL) << 48);
    n |= ((read(is) & 0xFFL) << 56);
    return n;
  }

  static void writeString(OutputStream os, String s) throws IOException {
    byte[] b = s.getBytes("UTF-8");
    writeLong(os, b.length);
    os.write(b, 0, b.length);
  }

  static String readString(InputStream is) throws IOException {
    int n = (int) readLong(is);
    byte[] b = streamToBytes(is, n);
    return new String(b, "UTF-8");
  }

  static void writeStringStringMap(Map<String, String> map, OutputStream os) throws IOException {
    if (map != null) {
      writeInt(os, map.size());
      for (Map.Entry<String, String> entry : map.entrySet()) {
        writeString(os, entry.getKey());
        writeString(os, entry.getValue());
      }
    } else {
      writeInt(os, 0);
    }
  }

  static Map<String, String> readStringStringMap(InputStream is) throws IOException {
    int size = readInt(is);
    Map<String, String> result = (size == 0)
        ? Collections.<String, String>emptyMap()
        : new HashMap<String, String>(size);
    for (int i = 0; i < size; i++) {
      String key = readString(is).intern();
      String value = readString(is).intern();
      result.put(key, value);
    }
    return result;
  }


}
